Answer:
{800, 400, 200, 100, 50, 25}
Step-by-step explanation:
Look at the last three numbers. Notice that each is half of the previous number: 50 is half of 100, etc.
Thus, the number preceding 100 must be 200; the one before that is 400, and the first number is 800.
Thus the sequence is {800, 400, 200, 100, 50, 25}